The broad goal of this project is to lay the foundation for research identifying salivary biomarkers that are predictive of the vulnerability of individuals to (a) progress toward nicotine dependence and (b) ultimately to become dependent on nicotine by emerging adulthood, given their exposure to life stress. Features of the proposed research is the use of an interview-based life stress assessment to provide a precise and reliable measurement of chronic and episodic stress, and initial steps in the identification of easily obtained salivary biomarkers that identify individuals who are exposed to greater levels of chronic stress. This project has the potential to advance drug abuse prevention and intervention research through identifying Genetic x Environment (GxE) interactions, which may help to explain the success or failure of interventions designed to prevent the initiation of tobacco use and the progression to nicotine dependence, or to maintain cessation. The proposed assessment with two cohorts at age 20/21 (n = 390) includes saliva collection for DNA extraction to assess polymorphisms of candidate genes known to be related to the stress-reward pathway, saliva collection for RNA extraction for candidate gene and genome wide gene expression, and a systematic contextual based assessment of chronic and episodic stress, using state-of-the-art assessment tools, at age 20/21. The data from this assessment will be integrated with other multi-source/multi-respondent data from two cohorts from an ongoing eleven-year longitudinal study examining the etiology of substance use, including nicotine dependence, combined with data assessing cortisol reactivity in response to laboratory induced stress, at age 20/21. To accomplish this broad goal, we propose to address the following aims: (1) Identify GxE interactions which predict change in nicotine dependence across from adolescence to emerging adulthood and across youth from the occurrence of polymorphisms of specified candidate gene known to be related to the stress reward pathway in the context of the experience of chronic and episodic stress;(2) Assess the association between specific genetic polymorphisms and cortisol reactivity in response to a laboratory induced stressor and assess the effect of GxE interactions on cortisol dysregulation through examining the effect of the interaction of genetic polymorphisms and life stress in emerging adulthood on cortisol dysregulation;and (3) Evaluate whether the salivary transcriptome contains RNA biomarkers for the identification of individuals with the gene expression signature of chronic stress using RNA samples from 24 individuals who experience the most life stress and 24 individuals with the least stress. We plan to validate an existing functional genomic signature of chronic stress previously identified in lymphocytes by performing gene expression analysis of individual candidate genes, and we will discover, confirm and validate novel candidate genes by performing genome-wide and candidate gene expression analysis. PUBLIC HEALTH RELEVANCE: This project has the potential to advance drug abuse prevention and intervention research through identifying Genetic x Environment (GxE) interactions, which may help to explain the success or failure of interventions designed to prevent the initiation of tobacco use and the progression to nicotine dependence, or to maintain cessation. Results may guide the selection of tailored interventions for specific individuals.